DVD players are known as apparatuses for playing back video contents such as movies and dramas. Navigation commands which are comparatively simple control language are used for controlling video playback in the DVD players. Meanwhile, in Blu-ray disc (BD) players which are gradually prevailing in recent years, Java virtual machines are adopted in order to make complicated and highly interactive contents viewable (see Patent Document 1). Furthermore, Java is a registered trademark (the same is true hereinafter).